FIELD BULLETIN NUMBER 30
                                    May 1984

        The following is being made available for those of you who do not
        have the TS 803, TS 803H, and the TPC I User's Manuals' Addendum,
        dated 15 Feb. 84,  and  may need modem port initialization infor-
        mation.

             TS 803, TS 803H, TPC I: INPUT FROM MODEM PORT

        The modem port of the TeleVideo TS 803 (after BIOS level 1.3), TS
        803H (all BIOS levels), and TPC I (all BIOS levels) is interrupt-
        driven  and  buffered by the BIOS.   The following functions have
        been added to the BIOS to provide user  program  interface  (note
        that  the  BIOS  is  called  via RST 6 with register C set to the
        desired function's index):

        o     Character ready status check:     C = 18
                  Returns:  Z flag set if no characters are ready
                  Example:

                       STAT:   MVI  C,18     ; Set C for status check
                               RST  6        ; Call BIOS
                               JZ   STAT     ; No Chars ready

        o     Retrieve available character:     C = 19
                  Returns:  Z flag clear if a character is ready
                            register A contains next defined character
                  Example:

                       GETC:   MVI  C,19     ; Set C for retrieval
                               RST  6        ; Call BIOS
                               JZ   GETC     ; Optional: no previous
                                               status check
                                             ; register A contains
                                               character

        o     Initialize the modem buffer:   C = 20
                                             HL = 0
                  Example:

                       INIT:   LXI  H,O      ; Clear HL
                               MVI  C,20     ; Set C for initialization
                               RST  6        ; Call BIOS

        NOTE:   Function 20 MUST be called before either function 18 or
                19 is called to ensure correct initialization of the BIOS
                buffer pointers.

        The proceeding is based on portions of the TS 803,  TS 803H,  and
        TPC I User's Manuals' Addendum, 15 Feb. 84 [125862-00 Rev. A].